Global warming vs collapsing AMOC

What if the AMOC collapsed?

Climate change can give rise to abrupt and unexpected outcomes in the Earth system. Last week, a new article in Nature Scientific Reports claimed that a collapse of the Atlantic Meridional Overturning Circulation (AMOC) could lead to a rapid cooling in the Northern Hemisphere, and that this cooling in turn could obliterate global warming for a period of 15-20 years. Only to revert to a warming pattern some 40 years later.

According to professor Sybren Drijfhout, his model showed that “The planet earth recovers from the AMOC collapse in about 40 years when global warming continues at present-day rates, but near the eastern boundary of the North Atlantic (including the British Isles) it takes more than a century before temperature is back to normal”.

Temperature anomaly in degrees Celsius after 95 years from the onset of an AMOC collapse. Source: Drijfhout (2015)

What is so scary about this study is that the effect of atmospheric cooling due to an AMOC collapse is associated with heat flow from the atmosphere into the oceans, which has actually occurred during the last 15 years. A well known fact to many scientists but somewhat unclear to the public which has been bombarded with climate deniers "warming hiatus" nonsense.

According to Drijfhout, when there is a net cooling effect heat flows from the oceans to the atmosphere but when there is net warming effect then this energy flow is reversed. In other words, the world’s oceans have acted as giant heat sinks, counteracting the greenhouse effect in regards to atmospheric temperatures, for the last decade. But this period is now over, according to Drijfhout. The oceans are again releasing heat, amongst others due to shifting ocean and wind patterns and a strong El Niño.